Define Newton's law of motion
2 answers:
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a) The length of the arm of the centrifuge is 10.9 m
b) The angular acceleration is
Explanation:
a)
In a uniform circular motion, the centripetal acceleration is given by
where:
is the angular speed of the circular motion
r is the radius of the circle
For the centrifuge in this problem, we have:
is the angular speed
The centripetal acceleration is 3.2 times the acceleration due to gravity (), so:
Therefore, we can re-arrange the previous equation to find r, the radius of the circle (which corresponds to the length of the arm of the centrifuge):
b)
In the second part of the exercise, the centrifuge speeds up from an initial angular speed of 0 to a final angular speed of 1.7 rad/s. The total acceleration experienced at the final moment is
So, 4.4 times the acceleration due to gravity.
The total acceleration is the resultant of the centripetal acceleration () and the tangential acceleration (
):
We know that:
a = 4.4g
So, we can find the tangential acceleration:
The angular acceleration is related to the tangential acceleration by
where r = 10.9 m is the length of the centrifuge. Substituting,
Learn more about centripetal and angular acceleration here:
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Answer:
y = 67.6 feet, y = 114.4/ (22 - 3t)
Explanation:
For this exercise let's use that light travels in a straight line and some trigonometric relationships, the symbols are in the attached diagram
Large triangle Projector up to the screen
tan θ = y / L
For the small triangle. Projector up to the person
tan θ = y₀ / (L-d)
The angle is the same, so we equate the two equations
y₀ / (L -d) = y / L
y = y₀ L / (L-d)
The distance from the screen (d), we look for it with kinematics
v = d / t
d = v t
we replace
y = y₀ L / (L - v t)
y = 5.2 22 / (22 - 3 t)
y = 114.4 (22 - 3t)⁻¹
This is the equation of the shadow height change as a function of time
For the suggested distance the shadow has a height of
y = 114.4 / (22-13)
y = 67.6 feet
